Book Image

Learning Linux Shell Scripting

By : Ganesh Sanjiv Naik
Book Image

Learning Linux Shell Scripting

By: Ganesh Sanjiv Naik

Overview of this book

Linux is the one of the most powerful and universally adopted OSes. Shell is a program that gives the user direct interaction with the operating system. Scripts are collections of commands that are stored in a file. The shell can read this file and act on the commands as if they were typed on the keyboard. Shell scripting is used to automate day-to-day administration, and for testing or product development tasks. This book covers Bash, GNU Bourne Again SHell, preparing you to work in the exciting world of Linux shell scripting. We start with an introduction to the Shell environment and explain basic commands used in Shell. Next we move on to check, kill, and control the execution of processes in Linux OS. Further, we teach you about the filter tools available in Linux and explain standard output and standard errors devices. Then we will ensure you understand Shell’s interpretation of commands and get a firmer grasp so you use them in practice. Next, you’ll experience some real-world essentials such as debugging and perform Shell arithmetic fluently. Then you’ll take a step ahead and learn new and advanced topics in Shell scripting, such as starting up a system and customizing a Linux system. Finally, you’ll get to understand the capabilities of scripting and learn about Grep, Stream Editor, and Awk.
Table of Contents (20 chapters)
Learning Linux Shell Scripting
Credits
About the Author
Acknowledgments
About the Reviewers
www.PacktPub.com
Preface
Index

Process management


Since we have understood the command to check processes, we will learn more about managing different processes as follows:

  • In a Bash shell, when we enter any command or start any program, it starts running in foreground. In such a situation, we cannot run more than one command in the foreground. We need to create many terminal windows for starting many processes. If we need to start many processes or programs from the same terminal, then we will need to start them as background processes.

  • If we want to start a process in the background, then we need to append the command in the Bash shell by &.

  • If I want to start my program Hello as the background process, then the command would be as follows:

    $ Hello &
    
  • If we terminate any command by &, then it starts running as the background process.

For example, we will issue a simple sleep command, which creates a new process. This process sleeps for the duration, which is mentioned in the integer value next to the sleep command...